It is proposed to investigate the response of visual pigments from specially selected vertebrates to mild treatments such as temperature, inorganic ions and specific organic substances. This will be done (1) with the pigments solubilized in various nonionic and ionic detergents and (2) with the pigments in situ within the outer segments. For the latter study the outer segments will be deposited on a glass slide with the Cytospin Centrifuge, treated in specific ways as required, and then analyzed spectrophotometrically. With this technique the role of water in the responses can be assayed since the analysis can be made with the deposited cells either moistened or dried to varying degrees. Additionally, the spectra of single outer segments can be determined with the microspectrophotometer at Cornell. Animals will be chosen whose pigments have already been shown to possess unique and useful properties in their responses to mild treatment or else for some special biological or medical reason. Such animals will include geckos and lizards related to geckos, the Arctic cod and other available cold water fishes, hot water fishes, lampreys and rats with an hereditary dystrophic pathology of the retina. A continued search will be made to discover new animals whose pigment systems respond in unique or unexpected ways. The general aim, of course, is to determine the physiological role, other than light capture, of the retinal photopigments including the maintenance of integrity of the outer segment.